Some parts of the Obj-C API have been divided in another framework : ReactiveObjC.

I needed to install this framework to access these methods.

Solution :

As stated in README (Objective-C and Swift section), those Objective-C
API are splitted out to ReactiveObjC framework. You need to add
https://github.com/ReactiveCocoa/ReactiveObjC as a submodule, link the
framework, then import ReactiveObjC.